At present an individual can be specified by biometrics authentication in which a living body is an object of authentication. For example, authentication by palm or finger veins (vein authentication) is easy to use, so it has spread in places which ordinary people use as an authentication method which provides great security.
With the vein authentication near-infrared light is used for capturing an image of the pattern of palm or finger veins and a vein pattern acquired by the image capture is compared with a vein pattern registered in advance. If the vein pattern at registration time matches the vein pattern acquired by the image capture at authentication time with determined accuracy, then an identity is confirmed (see, for example, Japanese Laid-open Patent Publication No. 2007-229360 and Japanese Laid-open Patent Publication No. 2007-233231).
When an image of a vein pattern is captured, it is necessary to place a palm or a finger at a determined position with respect to an image capture apparatus. Accordingly, a position at which a palm or a finger is placed at registration time may differ from a position at which the palm or the finger is placed at authentication time. In this case, an image of the vein pattern captured at registration time differs from an image of the vein pattern captured at authentication time. As a result, in spite of the vein pattern of the same person, the erroneous determination that an image of a vein pattern of another person is captured at authentication time may be made.
In order to avoid such an authentication failure, a method for making a positional correction of a vein pattern acquired by image capture at authentication time before comparison is proposed. For example, a method for acquiring vein characteristic information by capturing an image of a vein pattern at authentication time, making a positional correction of the vein characteristic information by the use of characteristic information for wrinkles in a finger acquired by image capture through the use of visible light, and making a comparison by the use of the vein characteristic information after the correction is known (see, for example, Japanese Laid-open Patent Publication No. 2008-134862).
It is assumed that, like the method disclosed in the above Japanese Laid-open Patent Publication No. 2008-134862, corrected information is used for making a comparison. However, if the amount of vein characteristic information acquired is smaller than that of registered information, the reliability of authentication itself cannot be improved. That is to say, in order to improve the reliability of authentication itself, it is necessary to perform authentication by making vein patterns acquired by image capture at registration time and authentication time match with great accuracy. Accordingly, it is necessary to increase reproducibility so that the position of a living body with respect to an image capture apparatus at authentication time will match the position of the living body with respect to the image capture apparatus at registration time as closely as possible.